Alert archive / Montana / Mesoscale Discussions in 2016

Mesoscale Discussion 1321

July 18, 20165 counties in Montana

The Storm Prediction Center issued this mesoscale discussion at Jul 18, 2016, 4:01 PM MDT for 5 counties in Montana. It was in force for 89 min.

The area

The outline as issued.

The facts

Issued
Jul 18, 2016, 4:01 PM MDT (22:01 UTC)
Expired
Jul 18, 2016, 5:30 PM MDT
In force
89 min
Issued by
the Storm Prediction Center
Chance of a watch
20%

Counties Cascade County, MT, Flathead County, MT, Lake County, MT, Lewis and Clark County, MT, Teton County, MT

The radar

The Missoula radar (KMSX), 105 km from the middle of the area, began a volume at 22:01 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Great_falls, MT (KTFX), launched 12:00Z, 10.0 hours before the alert went out and 172 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Great_falls, MT at 12:00Z on 2016-07-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 20 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Great_falls, MT at 12:00Z on 2016-07-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -11 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
20 J/kg
Mixed-layer CIN
-342 J/kg
Mixed-layer LCL
1233 m above ground
0-6 km bulk shear
57 kt
0-1 km storm-relative helicity
-11 m²/s²
0-3 km storm-relative helicity
121 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.4

Open this sounding in Storm Lab

The text

As transmitted.

396 
ACUS11 KWNS 182201
SWOMCD
SPC MCD 182201 
MTZ000-182330-

MESOSCALE DISCUSSION 1321
NWS STORM PREDICTION CENTER NORMAN OK
0501 PM CDT MON JUL 18 2016

AREAS AFFECTED...W CENTRAL AND NW MT

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 182201Z - 182330Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...A FEW THUNDERSTORMS WILL DEVELOP OVER THE HIGH TERRAIN AND
SPREAD NEWD THIS EVENING.  ISOLATED HAIL AND STRONG OUTFLOW WILL BE
POSSIBLE WITH THE STRONGEST STORMS...BUT STORM COVERAGE/INTENSITY
WILL LIKELY REMAIN TOO LOW FOR A WATCH.

DISCUSSION...STRONG SURFACE HEATING OVER THE HIGH TERRAIN IN WRN MT
IS BEGINNING TO SUPPORT THUNDERSTORM DEVELOPMENT W OF HELENA AND
KALISPELL.  THE CONVECTION IS ROOTED IN A STEEP LAPSE RATE
ENVIRONMENT WITH SUFFICIENT DEEP-LAYER VERTICAL SHEAR FOR
SUPERCELLS...DOWNSTREAM FROM THE MIDLEVEL TROUGH OVER THE PAC NW
COAST.  SINCE THE CONVECTION APPEARS TO BE TIED PRIMARILY TO TERRAIN
CIRCULATIONS...RATHER MODEST MOISTURE/BUOYANCY AND REMAINING
CONVECTIVE INHIBITION ACROSS THE LOWER ELEVATIONS CAST DOUBT ON
STORM COVERAGE/INTENSITY THE REMAINDER OF THE EVENING.  WILL
CONTINUE TO MONITOR THIS AREA...BUT OVERALL EXPECTATIONS ARE TOO
MARGINAL TO WARRANT A SEVERE THUNDERSTORM WATCH.

..THOMPSON/GRAMS.. 07/18/2016

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...TFX...MSO...

LAT...LON   47761183 47421126 47001111 46741120 46531144 46451180
            46621219 47001280 47511431 47911484 48371502 48611488
            48781451 48851421 48101314 47911253 47761183

Nearby

Mesoscale Discussions in Montana, 2016Every mesoscale discussion in 2016

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.